Process for the pyrolytic conversion of normally gaseous aliphatic hydrocarbons



March 1,1932- G. G. OBERFELL ET AL.

PROCESS EGR THE PYROLYTIC-CONVERSION OF NORMALLY GASEOUS ALIPHATIC HYDROCARBONS Filed May 24. 1928 NEY Patented Mar. 1, 1932 l UNITED STATES PATENT OFFICE GEORGE G. OBEBFELL, JESSE A.

OKLAHOMA, ASSIGNORS TO PHILLIPS PETROLEUM COMPANY,

GUYEBfAND FREDERICK E. FREY, F BARTIESVILLE,

OF BABTLESVILLE,

OKLAHOMA, A CORPORATION 0F DELAWARE PROCESS HYDBOCARBONS Application. led May 24, 1928. Serial No. 280,333.

This invention relates to the treatment of gaseous hydrocarbons and particularly to a multi-stage process for partially reforming such hydrocarbons and producing liquid hydrocarbons. l

The primary object of the invention is to provide a multi-stage process in which gaseous hydrocarbons such as light natural gas constituents, are reformed into other gases and also converted into liquid hydrocarbons.

It has heretofore been proposed to subject gaseous hydrocarbons to cracking temperature at sullicient velocity to reform such hydrocarbons and convert some of same into liquid hydrocarbons. In these prior proposals, the hydrocarbons treated have been heated in various ways and in some instances the reformed hydrocarbons have been recycled through the reaction chamber with a view of treating the reformed hydrocarbons a second time.

In the process forming the subject matter l of the present application, the gaseous hydrocarbons are treated aplurality oftimes under conditions of time andtemperature in such manner as to partially reform the same and "produce liquid hydrocarbons. In a modllication of such process the gaseous hydrocarbons are first subjected to cracking in one reaction chamber and the resulting reformed gases and liquid hydrocarbons are passed through a separating apparatus, from which the reformed gases are passed through a second reaction chamber with ing the character of the reformed gases so treated and producing an additional amount of liquid hydrocarbons.

In the present invention a plurality of treating units are used, and as anjexample a pure gas such as propane or a mixture of hydrocarbon gases, are treated in two or more stages without the addition of any untreated gases or `recycled gases. The raw gas is treated in the first unit at a temperature and time of exposure somewhat lower than that required for the maximum yield of benzol in a singl' treatment. That is, instead of pushin the recovery of benzol to its limit in the rst cracking unit, the reaction is interrupted at an -optimum output of benzol, cona view of changsidered as such by what will produce a maximum overall yield of benzol, and with as little formation of tar andv other deleterious products, as possible. In this Way, the series of chemical reactions are only partly completed in the first unit, the reactions producing tar and carbon proceeding in this unit to a slight extent only. The benzol produced is removed in the first benzol recovery unit and the reformed gas is sent to the second treating unit, Where it is again treated under conditions most favorable to that type of gas. The treatment in the second unit may be the same or different from that used in the first unit and if the gas is not stripped of its benzol in the second unit, it may be again treated in a similar' third unit.

'In this process, the gases such as propane and butane in the first unit, may be cracked under such conditions as to cause certain reactions only, and the gas is then removed from the reaction chamber before further reactions take place. If the resulting liquid hydrocarbons are separated from the reformed gas, the latter may be treated in the second unit to complete the reactions commenced in the first unit or to cause different reactions in the second unit.

The process may also be operated to produce an optimum yield of liquid hydrocarbons in each stage of the process. It is especially adapted to the continuous refining, with accompanying extraction of by-products, of batches of hydrocarbon gases having boiling points below and adjacent to 50 degrees F., such as the raw gases within that range occurring in natural gas, considerable condensate recovery, particularly benzol, and its derivatives. The recovery of these liquids is so desirable that the multi-stage treatment, giving entire freedom of derivative control in each stage, as governed by the relative amounts extracted, temperature and period of reaction, has been found for some purposes to give much superior results to running the system as a recycling one.

The invention will now be described in detail in connection with the accompanying drawing which shows a diagrammaticview which offer a stance, butane, propane, ethaiie, methane, or

mixtures thereof, will be introduced into the system at the point A and after flowing through a suitable pressure regulator will be metered at B. These gases pass through the heat exchanger C in which they are preheated chamber, and the gases to be treated, leave the heat exchanger by way of pipe D and flow through a coil or coils E arranged in a suitable heater S. In the coil E'the processed gases are additionally heated to below the cracking temperature of the same and then they are fed through a tube or tubes F where their temperature is raised to the cracking point. From the tubes, the gases flow into the reaction chamber G and dueto the heating impaited to the same in the tubes F, the gases undergo reactions which may be controlled by the degree of heat imparted in the heater S and the time of exposure within the reaction chamber. In one embodiment of the invention only certain reactions are permitted to take place in the reaction chamber and this results in a reformation of some of the gases and conversion of some of the same into liquid hydrocarbons. The gaseous mixture leaving the reaction chamber by way of conduit C1 passes through the heat exchanger C and loses some of its heat to the incoming gas and in this way the reformed gases and the liquid hydrocarbons whichthey carry are partially cooled.

From the heat exchanger the last mentioned gases and liquids pass through conduit C2 into a suitable purifier or scrubberl H in whi-ch tar and carbon are removed while the gases are additionally cooled. From the scrubber the gases pass by way of conduit H1 into a suitable extracting plant I in which the reformed -gases are separated from the liquid hydrocarbons (benzol), the latter being discharged through the pipe H2.

The reformed gases now pass through pipe J to an apparatus of the same character as that just described, and in this apparatus I is the heater, O the reaction chamber, K the seat exchanger, P the scrubber, and Q the separating plant. In the second unit L indicates the pipe for passing the reformed gases to the second heating coils and M and N indicate the tubes in which the reformed gases are subjected to cracking temperature.

The heaters are preferabl fired by means of gas burners, and U and indicate respectively the stacks of the furnaces.

The residue gases from the process are discharged through the pipe R. The temperatures maintained within the reaction chambers G and O will be within a range of 12500 F. to 1750 F. and it is obvious that by varying the temperatures in the reaction chamy the reformed gases from the reactionv bers and varying the exposure time of the reaction products within these chambers, different results may be produced.

If desired conditions may be such in the reaction chamber (Jr that only certain reactions will take place and a quantity of benzol will be produced therein, while in the reaction chamber U the reaction may be completed and another quantity of benzol may be obtained.

Un the other hand, it is evident that coni ditions may be suoli in the first reaction chamber as to produce an optimum yield of benzol therein and conditions may also be maintained in the second reaction chamber to also produce an optimum yield of benzol in that chamber.

When this system is used for the treatment ot' natural gas hydrocarbons, it is preferably employed with gases of this character from which pentanes and heavier hydrocarbons have been substantially removed.

Instead of using two furnaces or heaters, a single furnace may be employed and in such case the heating coils E and nl and the tubes F and N will be arranged in the furnace in proper locations to permit variations of temperature on the material passed through the respective reaction chambers Gr and O.

lt will be obvious to those skilled in the art that various changes may be made in the details disclosed without departing from the spirit of the invention as expressed iii the claim.

What is claimed and desired to be secured by Letters Patent is:

In a process for the pyrolytic conversion of normally gaseous aliphatic hydrocarbons to crude benzol, heating said gaseous hydrocarbons to a reforming temperature between 12500 and 1750o F. in an elongated passageway of restricted cross-sectional area, passing the heated gaseous hydrocarbons into an enlarged zone, maintaining without any addition of heat, the heated gaseous hydrocarbons in the said zone for a time-temperature to produce less than the maximum yield of crude benzol, separating the crude benzol so produced from the residual gas, then passin the residual gas through a second elongate passageway of restricted cross-sectional area while heating the residual ture between 1250 and 1750o F., passing the heated residual gas from the second passageway into a second enlarged zone, maintaining the heated residual gas in the second enlarged zone for a time-temperature to produce the optimum yield of crude benzol Without applying additional heat to the said residual gas, and then separating additional crude benzol from the residual gas.

GEORGE G. OBERFELL. FREDERICK E. FREY. JESSE A. GUYER. 

